This invention is generally directed to toner and developer compositions. More specifically, the present invention is directed to toner compositions containing therein a low molecular weight wax, such as polyethylene, or polypropylene, and crosslinked copolymer resinous particles. Therefore, in accordance with one embodiment of the present invention there are provided toner and developer compositions having incorporated therein a low molecular weight wax, including polyethylene, and polypropylene, and a polyblend mixture of a crosslinked copolymer composition, and a second polymeric composition. Also, the toner compositions of the present invention can contain therein charge enhancing additives for the purpose of imparting positive charges to the toner resin particles enabling the use of these compositions in imaging systems wherein the photoreceptor imaging member is negatively charged. The toner and developer compositions of the present invention are useful in affecting the development of images in electrostatographic imaging systems wherein an offset preventing liquid, such as a silicone oil is not required.
Toner and developer compositions with waxy materials are known. Thus, for example, there is described in British Pat. No. 1,442,835 a toner composition comprised of a styrene homopolymer or copolymer resin, and at least one polyalkylene compound selected from polyethylene and polypropylene. According to the disclosure of this patent, reference page 2, beginning at line 90, the starting polymer resin may be either a homopolymer of styrene, or a copolymer of styrene with other unsaturated monomers, specific examples of which are disclosed on page 3, beginning at line 1. Polyalkylene compounds selected for incorporation into the toner compositions disclosed in this patent include those of a low molecular weight, such as polyethylene, and polypropylenes of an average molecular weight of from about 2,000 to about 6,000.
Additionally, there is disclosed in a copending application U.S. Ser. No. 434,198, now U.S. Pat. No. 4,460,672, entitled "Positively Charged Toner Compositions", a developer composition mixture comprised of electrostatic toner particles consisting of resin particles, pigment particles, a low molecular weight waxy material with a molecular weight of from about 500 to about 20,000, and further included in the composition from about 0.5 percent by weight to about 10 percent by weight of a charge enhancing additive selected from, for example, alkyl pyridinium halides, organic sulfonate compositions, and organic sulfate compositions. The disclosure of this copending application is totally incorporated herein by reference.
Also, there is disclosed in U.S. Pat. No. 4,206,247, a developer composition comprised of a mixture of resins including a low molecular weight polyolefin and alkyl modified phenol resins. More specifically, it is indicated in this patent, reference column 4, line 6, that the invention is directed to a process which comprises the steps of developing an image with toner particles containing in certain proportions at least one resin selected from group A, and at least one resin selected from group B, wherein the resins of group A include a low molecular weight polyethylene, a low molecular weight polypropylene, and similar materials, and wherein the group B resins include natural resin modified maleic acid resins, and natural modified pentaerythritol resins. As examples of group A resins there is mentioned polystyrene, styrene series copolymers, polyesters, epoxy resins, and the like, reference the disclosure in column 5, line 47. The molecular weight of the polypropylene, or polyethylene used is from about 1,000 to about 10,000, and preferably from about 1,000 to about 5,000.
Moreover, developer compositions with charge enhancing additives, especially additives which impart a positive charge to the toner resin are well-known. Thus, for example, there is described in U.S. Pat. No. 2,986,521, reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica. Additionally, in U.S. Pat. No. 3,893,935 there is described the utilization of certain quaternary ammonium salts as charge control agents for electrostatic toner compositions. In accordance with the disclosure of this patent, certain quaternary ammonium salts, when incorporated into a toner material, were found to provide a particular toner composition which exhibited relatively high uniform stable net toner charge when mixed with a suitable carrier vehicle, which toner also exhibited a minimum amount of toner throw off. There is also described in U.S. Pat. No. 4,298,672 positively charged toner compositions comprised of resin particles, and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds and their hydrates of the formula as detailed in column 3, beginning at line 14. Examples of alkyl pyridinium compounds disclosed include cetyl pyridinium chloride. Also, there is disclosed in U.S. Pat. No. 4,338,390 positively charged developer compositions and organic sulfate, and sulfonate compositions as charge enhancing additives.
Developer compositions can be selected for use in developing electrostatic images, wherein the toner image is fixed to a permanent substrate such as paper by contacting the paper with a roller, the surface of which is formed from a material capable of preventing toner particles from sticking thereto. In this process, however, the surface of the fixing roll is brought into contact with the toner image in a hot melt state, thus a part of the toner image can adhere to and remain on the surface of the roll. This causes a part of the toner image to be transferred to the surface of a subsequent sheet on which the toner image is to be successively fixed, thereby causing the well-known undesirable offset phenomena.
In order to substantially eliminate offsetting, and more specifically for the purpose of preventing adhesion of the toner particles to the surface of the fixing roller, there has been selected certain types of rollers, the surface of which may be covered with a thin film of an offset preventing liquid such as a silicone oil. These oils are highly effective, however, the apparatus within which they are incorporated is complicated and costly since, for example, a means for feeding the oil is required. Also, not only do the silicone oils emit an undesirable odor, but these oils deposit on the machine components causing toner particles to collect on, and adhere to the silicone oils, which is highly undesirable. An accumulation of toner particles on machine components is troublesome in that image quality is adversely affected, and these components must be periodically cleaned and/or replaced, adding to the maintenance costs of the machine system involved.
Accordingly, there is a need for toner and developer compositions, especially those compositions with crosslinked resins which are useful in electrostatographic imaging systems. Additionally, there continues to be a need for improved toner and developer compositions which can be selected for the development and fixing of electrostatic latent images in electrostatographic imaging devices wherein offset preventing liquids, such as silicone oils, are not required. Furthermore, there is a need for toner and developer compositions comprised of a polyblend mixture of crosslinked copolymers and a second polymer. Moreover, there remains a need for toner and developer having incorporated therein low molecular weight waxes functioning as a release material. Furthermore, there remains a need for positively charged toner compositions comprised of a polyblend mixture of resin particles and low molecular weight waxes functioning as release components.